Patent GB-916501-A (GB)
Title: Machine tool
IPC: B23Q41/00
Filed: 1959-06-17
Abstract: 916,501. Electric programme control systems. KEARNEY & TRECKER CORPORATION. June 17, 1959 [June 27, 1958; March 30, 1959], No. 20770/59. Class 38 (6). [Also in Group XXII] A machine-tool comprises a tool storage means 70, Figs. 1 and 20D, carrying a plurality of tools for placement in an operating station 62 and a tool change arm 71 carried by the frame of the machine to place a tool in the operating station from the storage means. The tool storage magazine 70 is carried by the saddle, is rotated by an hydraulic motor 130, Fig. 5, and contains the tools 65 each having a different cutter 68. During cutting, the tool change arm 71 is swung through 90 degrees to an inoperative position by an hydraulic unit 72. The arm has two tool grips 75, Fig. 37, containing rollers 77 for engaging collars 119 on the tools. As the arm is swung back to its operative position, the next selected tool is swung out of the magazine. The hydraulic means 72 then rotates the arm, by an hydraulic rack-piston 284, Fig. 11, engaging a a gear 282, to grip the two tools, advances the arm by an hydraulic means 301 attached to a splined sleeve 290 to retract the tools from their holders, rotates it clockwise to interchange the tool positions, retracts it to place the tools in their new holders, and then moves it back to its inoperative position. To obtain the four angular positions of the arm, the piston 284 is acted upon selectively at each end by a plunger and a coaxial annular piston. The positions are indicated electrically by a cam 355, Fig. 13, rotated with the gear 282 and grooved to co-operate with switch rollers 348A, 349A, 350A. Alternate initial swinging movements of the arm take place in opposite directions. Each tool consists of a sleeve 116, Fig. 17, having a locating plug 117 abutted by a cutter 68 clamped by a collet 118 engaged by the collar 119. The collar 119 bears up to five strips 135 which identify the thirty-one tools (one in the spindle and thirty in the turret) by a binary code. The strips are " read " at the tool change station 105, Fig. 4, by sliding or pivoted arms 141 operating spring contacts. (In a modification, the collar 119, Fig. 34, is connected to ground and has a land in one or other half of five peripheral regions 641-645, so that the contacts 651A-655A, 651B-655B are positively operated.) When the desired tool is located by the reading means, the magazine over-runs slightly; the motor 130 is therefore reversed and exhausts through a throttle valve so that the magazine rotates at a slow speed. While the magazine is rotating forwardly, pressure to the motor operates a plunger 163 to hold a spring-pressed switch-operating arm 157 clear of a stop-switch 162. When the motor is reversed, the arm is released and stops the magazine as soon as flats on a shaft 161 allow the arm to be pressed against the switch. Due to the reversal, the strips identifying the tool are " read " twice. If, for any reason, the second reading shows that the correct tool has not been selected, the magazine will rotate again until the correct tool is found. If the correct tool is already in the spindle or at the tool change station, no rotation of the magazine occurs. If the tool 65 carries a tap 427, Fig. 19, it abuts a rod 450 connected by rods 454, 480, to a cam 481 controlling switches 425, 426. The tap-holder 433 is centralized in the tool by springs 436, 437 and if the spindle is fed too quickly or slowly, one or other of the switches is actuated to control the feed speed. If excessive resistance to the tap occurs, both switches are actuated and the machine is stopped. The machine is operated manually through switches or automatically under the control of punched or magnetic tape, the various machine parts carrying abutments to signal the completion of their movements. The speeds of the hydraulic motors feeding and rotating the spindle are controlled manually by potentiometers connected to servo-valves or, if automatic tape control is used, the valves are set by voltages read from the tape. The feed-rate servo-valve is further controlled if tapping is to take place by bringing into circuit a voltage control comprising a series of resistors so that the feed is at the correct speed for the pitch of thread to be cut. The voltage is obtained from a tachometer generator driven by the spindle as it rotates. Resistors in the generator circuit are controlled by the switches 425, 426. The tool may have integral or detachable identifying rings 930, Fig. 40, retained by a nut 932. In a further modification, the identifying means consist of indentations 947, Fig. 49, on the drill itself, the drill being located in the magazine by means of flats 952. Specifications 916,502, 916,503 and 916,504 are referred to.